1. Field of the Invention
The present invention relates to a tool holder for, for example, a hammer drill.
2. Description of the Related Art
Recently, some tool holders enable a user to attach the bit onto a power tool without manipulating a tool sleeve. Such tool holders include a tool-holding tube that the bit is inserted into and an engagement member that engages in a groove formed in the bit in order to prevent the bit from pulling out of the tool-holding tube. The engagement member is disposed in an elongated hole that follows the axial direction of a tool-holding tube. When a bit is inserted to a sufficient extent into the tool-holding tube, the engagement member moves in the radial direction of the tool-holding tube into engagement with the groove of the bit.
For example, Japanese Patent-Application Publication No. HEI-3-43003 discloses a tool holder with a tool-holding tube and a ball as an engagement member. The ball is movable within an elongated hole formed in the tool-holding tube so as to extend in the axial direction of the tool-holding tube. Also, a spring is interposed between the tool-holding tube and a tool sleeve of the tool holder. The spring urges the ball toward the tip of the tool holder in the axial direction of the tool-holding tube.
After the tool holder has been assembled together, the ball protrudes into the bit insertion hole of the tool-holding tube, that is, inward more than the inner peripheral surface of the tool-holding tube. When a bit is inserted from the tip of the tool holder, the rear tip of the bit contacts the ball and presses the ball away from the tip of the tool holder against the urging force of the spring. While the ball moves away from the tip of the tool holder, the ball also moves outward in the radial direction of the tool-holding tube so that the bit can be further inserted into the bit-insertion hole of the tool-holding tube. At this point the ball is pressed by the spring against the outer peripheral surface of the bit. When the bit is inserted until the groove formed in the bit is aligned with the ball, the urging force of the spring moves the ball inward in the radial direction of the tool-holding tube into engagement with the groove of the bit. In this way, the bit can be mounted on the tool holder without manipulating the tool sleeve.
Japanese Patent-Application Publication No. HEI-9-70772 discloses a tool holder with a key as an engagement member. A regulating sleeve, which is slidable in the axial direction of the tool-holding tube, is interposed between the tool-holding tube and the tool sleeve. The regulating sleeve regulates movement of the key in the radial direction of the tool-holding tube. Also, a stopper spring is provided for regulating sliding movement of the regulating sleeve.
When the bit is inserted from the tip of the tool holder into the bit-insertion hole of the tool-holding tube, the bit abuts against and pivots the stopper spring. The pivoting movement of the stopper spring presses the regulating sleeve in the opposite direction of movement of the bit, that is, toward the tip of the tool holder. This movement of the regulating sleeve moves the key inward in the radial direction of the tool-holding tube into engagement with the groove of the bit. In this way, the stopper spring allows the regulating sleeve to move forward when the bit is inserted into the tool holder, but prevents the regulating sleeve from moving backward when the bit is pulled outward from the central hole of the tool-holding tube. As a result, the bit can be mounted in the tool holder without manipulating the tool sleeve.
However, the tool holder described in Japanese Patent-Application Publication No. HEI-3-43003 can be troublesome to assemble and disassemble. For example, when the tool holder is being assembled, the ball can accidentally fall out from the elongated hole. Also, when the tool holder is being disassembled, the spring can flip the ball out.
The tool holder described in Japanese Patent-Application Publication No. HEI-9-70772 is also troublesome to assemble and disassemble in the same manner as described in Japanese Patent-Application Publication No. HEI-3-43003. That is, when the tool holder is being assembled, the key can accidentally fall out from the elongated hole. Also, when the tool holder is being disassembled, the spring can flip the key out. The tool holder described in Japanese Patent-Application Publication No. HEI-9-70772 additionally has a complicated overall configuration because of the stopper spring and other required components. Furthermore, the tool holder is likely to be assembled incorrectly.
It is an objective of the present invention to provide a tool holder with a simple configuration that is easy to assemble and disassemble, that prevents the engagement member from falling out during assembly, and that prevents the engagement member from being flipped out during disassembly.
According to the present invention, a tool holder, for mounting a bit formed with a groove onto a power tool, includes a tool-holding tube, an engagement member, and a resilient member. The tool-holding tube defines a bit insertion hole that extends in an axial direction. The tool-holding tube is formed with an elongated hole that is in connection with the bit insertion hole and that extends in the axial direction. The engagement member is disposed in the elongated hole and partially protrudes into the bit insertion hole. The engagement member is movable, by abutment with and pressing force from the bit being inserted into the bit insertion hole, in the axial direction and, when located at a retraction position in the axial direction, also outward in a radial direction of the tool-holding tube. The resilient member is disposed to an outer periphery of the tool-holding tube at the retraction position. The resilient member increases in radial dimension from an initial state by pressure from the engagement member moving outward by pressing force from the bit. The resilient member resiliently returns to the initial state when pressure from the engagement member stops because the groove of the bit is located at the retraction position. As a result, the resilient member presses the engagement member inward in the radial direction into engagement with the groove of the bit.
With this configuration, the resilient member prevents the engagement member from falling our during assembly and from being flipped out during disassembly of the tool holder. As a result, assembly and disassembly can be easily performed with a simple configuration.
According to another aspect of the present invention, the resilient member is a thin-plate spring. With this configuration, only a small space is required for providing the resilient member to the outer periphery of the tool holder.
According to another aspect of the present invention, the thin-plate spring has an opening portion. Also, the tool-holding tube is provided with a stopper that protrudes into the opening portion of the thin-plate spring. The stopper prevents rotational movement of the thin-plate spring in a circumference direction of the tool-holding tube.
With this configuration, rotation of the thin-plate spring in the circumference direction of the tool holder can be prevented so that the bit can be reliably mounted and removed using the engagement member.